A review on gradient macroporous ceramic via powder-based direct foaming process

Abstract

Macroporous ceramics are potentially applicable in a wide range of industrial applications. The porous structure of macroporous ceramics is designed depending on the application of macroporous ceramics. This paper reviews gradient macroporous ceramics fabricated via powder-based direct foaming to produce a relatively dense surface and a highly porous body. The fabrication process and the characterization of such ceramics are also considered. In terms of fabrication, an overview of the direct-foaming and foaming conditions to obtain a uniform porous structure is described. With regard to characterization, the unique structure of porous ceramics and effect of the denser surface on the bending strength are summarized through the results of microstructural observation and three-point bending strength measurements. The presence of the surface layer enables an improvement in the bending strength while maintaining high porosity. The fabrication processes reviewed herein are highly promising for reducing the weight of porous ceramics while enhancing their mechanical strength.